Geohydrology and geotechnical aspects of dewatering of open tar sand mines along the Athabasca River (Canada)

Abstract

About 5% of the giant tar sand deposits along the Athabasca River in Western Canada can presently be mined by open-pit mining methods. Under certain conditions, groundwater depressions are created by continuous pumping to keep the tar sand mines dry. Groundwater depressions for plateautype mines are expected to expand beyond an area of 150 km2 after ten years. The volumes of groundwater flowing into a plateau-type open mine may range from 17,000-400,000 m3/day, depending on type of mining methods and the presence of water-tight clays. The Cretaceous tar sands are separated from underlying rock salt by a karstified Devonian limestone. Some of the groundwater flowing into an open mine consists therefore of saline waters and brines. Modern, but as yet unproven dredging methods may offer an economic alternative to 'dry' open-pit mining methods.